New Scientist - USA (2021-07-17)

(Antfer) #1

14 | New Scientist | 17 July 2021


News


NASA will attempt what has
been described as a “risky”
fix for the Hubble Space
Telescope after several weeks
of troubleshooting following
an unexpected shutdown.
Spacecraft tend to use
tried-and-tested technology.
The Hubble telescope’s payload
computer is a custom-designed
NASA Standard Spacecraft
Computer-1 developed in 1974. This
machine stopped communicating
with the telescope’s main
computer and caused a “safe
mode” shutdown on 13 June.
Since then, NASA engineers
have been conducting tests and
switching between main systems
and their redundant backups.
What was initially suspected to
be a memory problem with the
payload computer is now thought
to be a symptom of a power
supply failure or an issue with the
command unit that is the heart
of the telescope’s control system.
Engineers are only able to
issue commands via radio link
as the telescope orbits about
500 kilometres above Earth.
Now that the Space Shuttle has

been decommissioned, there
is no way to replace broken
components of the telescope.
The payload computer, power
supply and command unit sit
within a device known as the
Science Instrument Command
and Data Handling (SIC&DH) unit,
which controls and synchronises
all the experiments on board and
communicates with Earth. One
of the two original SIC&DH units

fitted to Hubble – the “A side”, as
NASA calls it – failed in 2008 and
was replaced during a Space
Shuttle mission. Since then,
Hubble has been running on the
original backup unit – the “B side”.
Paul Hertz at NASA says that
engineers have been switching in
bits of the A side replacement to
work out which part of the B side
has failed, but they haven’t found
the culprit. Now they will switch
in many more components of the
A side systems simultaneously
in an attempt to finally divert
around the broken component.

It is a “risky” move, he says,
because the current A side has
never been turned on in space.
“The only things we can try are
things that can be commanded.
You can’t actually put your hands
on and change hardware or take a
voltage, so that does make it very
challenging,” says Hertz.
There are long delays between
attempted fixes because engineers
have to go through each plan with
a fine-toothed comb to check
that no upgrade or change over
Hubble’s decades of operation
will cause problems. When they
have tested the plan on an exact
duplicate of the telescope on the
ground, it must be approved by
NASA management before it
can be tried for real.
Hubble was launched in 1990
at a cost of $4.7 billion and has
led to a series of discoveries
that helped determine the rate
of expansion of the universe.
“Eventually everything
breaks. The second one of
some redundant system will
fail,” says Hertz. “It’s like which
light bulb in your house is going
to burn out first.”  ❚

Matthew Sparkes

NA

SA

Technology

YouTube promotes
videos that violate
its own rules

YOUTUBE’S algorithm recommends
videos that violate the company’s
policies on inappropriate content,
according to a crowdsourced study.
Not-for-profit company Mozilla
asked users of its Firefox web
browser to install a browser
extension that tracked the YouTube
videos they watched, and asked
whether they regretted watching
each video. Between July 2020 and
May 2021, 37,380 users flagged

3362 such regrettable videos, a
fraction of 1 per cent of all those
they watched. Reports of these
were highest in Brazil, with about
22 videos out of every 10,
viewed being logged as regrettable.
Researchers watched the videos,
checking them against YouTube’s
content guidelines. About 12 per
cent of the reported videos
either shouldn’t be on YouTube, or
shouldn’t be recommended through
its algorithm, said the researchers;
about a fifth would be classified
as misinformation, and a further
12 per cent spread covid-
misinformation. Others had violent

or graphic content and hate speech.
“Some of our findings, if scaled
up to the size of YouTube’s user
base, would raise significant
questions,” says Brandi Geurkink
at Mozilla in Germany. “What we’ve
found is the tip of the iceberg.”
Most of the contentious videos
were delivered through YouTube’s
algorithm, which recommends
videos from channels that a user
may not follow or hasn’t searched

for. Seven in 10 of the regret reports
were tied to recommended videos,
which were 40 per cent more likely
to be regretted than videos users
actively searched for, says the team.
Non-English language videos
were 60 per cent more likely to be
regretted, which may be because
YouTube’s algorithms are trained on
primarily English-language videos.
A YouTube spokesperson said the
company had made changes to its
recommendations system in the
past year that reduced consumption
of “borderline content” to less
than 1 per cent of all videos. ❚
Chris Stokel-Walker

Astronomy

‘Risky’ fix planned for ageing Hubble


The space telescope malfunctioned unexpectedly last month, but a solution may be possible


“Scaled up to YouTube’s
user base, this raises
questions. We’ve found
the tip of the iceberg”

The Hubble Space
Telescope has been
in orbit since 1990
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